An improved design method for C-band photonic crystal fibers with flat near-zero dispersion
C波段具有平坦近零色散光子晶体光纤的一种改进设计方法

The innermost air holes of photonic crystal fibers deform easily during the draw process, resulting in serious influcence on the practical fiber dispersion. Based on the multipole method, the simulation in the paper only changes the air holes in the secondlayer and the third layer to adjust the dispersion, while the innermost air holes each are set to have a smaller parameter. The simulation shows that this simple dispersion control method can also make zero-dispersion point quickly move and keep the dispersion flat. Based on the detailed analysis, we propose C-band near-zero flat dispersion photonic crystal fiber with the dispersion coefficient varying from -0.24ps/(km ·nm) to 0.33 ps/(km ·nm). Simulation shows that the air holes increasing from the fifth layer have little influence on the dispersion of previously proposed fiber, So by increasing the layers of air holes we can obtain an ideal confinement loss. This method is also applicable for the design of PCF operating in S and L bands with similar properties.